The preleukemic syndrome: correlation of in vitro parameters of granulopoiesis with clinical features

The trajectory of prognostication and risk stratification for patients with myelodysplastic syndromes

ABSTRACT

Risk stratification and prognostication are crucial for the appropriate management of patients with myelodysplastic syndromes (MDSs) or myelodysplastic neoplasms, for whom the expected survival can vary from a few months to >10 years. For the past 5 decades, patients with MDS have been classified into higher-risk vs lower-risk disease phenotypes using sequentially developed clinical prognostic scoring systems. Factors such as morphologic dysplasia, clinical hematologic parameters, cytogenetics, and, more recently, mutational information have been captured in prognostic scoring systems that refine risk stratification and guide therapeutic management in patients with MDS. This review describes the progressive evolution and improvement of these systems which has led to the current Molecular International Prognostic Scoring System.

Secondary hematological changes mimicking the preleukemic syndrome. Report of two cases

Two women with hematological and clinical features typical of the preleukemic syndrome, including low marrow myeloid colony and cluster formation in vitro, showed unexplained spontaneous improvement with normalization of both peripheral blood values and in vitro cloning efficiency after 2-4 years. One patient had and the other developed later an autoimmune disorder. It is therefore suggested that secondary hematopoietic changes might have mimicked the preleukemic syndrome.

Enhanced growth of myelodysplastic colonies in hypoxic conditions

OBJECTIVE

To determine the response of bone marrow progenitor cells from patients with myelodysplastic syndromes (MDS) to culture in physiologic oxygen tension.

METHODS

Methylcellulose progenitor assays using both unfractionated bone marrow mononuclear cells (MNCs) and purified CD34(+) progenitors were performed in atmospheric oxygen (18.6% O(2)) or one of two levels of hypoxia (1% and 3% O(2)). Assays were performed using normal donor marrow, MDS patient marrow, acute myelogenous leukemia marrow or peripheral blood blasts, chronic phase chronic myelogenous leukemia (CML) marrow MNCs, and blast crisis CML peripheral blood.

RESULTS

The majority of MDS samples showed decreased colony-forming units (CFU) in 18.6% O(2) compared to normal controls, as expected. However, in either 1% or 3% O(2), 9 of 13 MDS samples demonstrated augmentation of CFUs beyond that observed in normal controls, with 6 of 13 demonstrating a greater than ninefold augmentation. This effect is cell autonomous, as it persisted after purification of CD34(+) progenitor cells. Additionally, the augmented response to physiologic oxygen tension is specific to MDS, as it was not observed in either acute or chronic myelogenous leukemia samples.

CONCLUSION

These results suggest that the reported decrease in MDS CFUs reflects greater sensitivity of MDS progenitors or their progeny to the nonphysiologic oxygen tensions routinely used in vitro, rather than a true decrease in progenitor frequency. Importantly, these experiments for the first time describe an experimental system that can be used to study the growth of primary cells from patients with MDS.

In vitro characterization of hematopoietic microenvironment cells from patients with myelodysplastic syndrome

In vitro studies on the functional integrity of the hematopoietic microenvironment in myelodysplasia have been controversial. Although some of them suggest that such a microenvironment is functionally normal, there is increasing evidence indicating that there are alterations in the function of microenvironment (adherent) cell layers from myelodysplastic syndromes (MDS) marrow. Adherent cell layers developed in vitro, however, consist of a mixture of different cell types-mostly fibroblasts and macrophages-thus, it is not clear which cell type(s) is(are) functionally abnormal in this disorder. In order to address this issue, in the present study, we first assessed some functional properties of MDS-derived adherent cell layers, as a whole, and then we analyzed those same functional properties after separating these cells into two different populations: a fibroblast-enriched cell layer and a macrophage-enriched cell layer. When whole adherent layers from MDS patients were analyzed, no significant differences were observed, as compared to their normal counterparts, in terms of morphology and total cell number. A major difference, however, was observed when analyzing the production of the cytokines interleukin-6 (IL-6) and tumor necrosis factor (TNF-alpha). Indeed, adherent layers from MDS patients produced higher levels of these cytokines (2- and 22-fold, respectively), as compared to normal layers. When fibroblast- and macrophage-enriched cell layers were analyzed, a higher apoptotic index was observed in those derived from MDS marrow (4% of TUNEL-positive cells in normal fibroblast layers versus 27% in MDS-derived fibroblast layers; 7% of TUNEL-positive cells in normal macrophage layers versus 24% in MDS macrophage layers). Macrophages from MDS marrow produced significantly higher levels of TNF-alpha (nine-fold) than their normal counterparts. MDS-derived fibroblasts, on the other hand, produced higher levels of IL-6 (nine-fold), as compared to normal fibroblasts. Surprisingly, whereas normal fibroblasts showed a discrete production of TNF-alpha, we found a very high production of this cytokine in cultures of fibroblasts from MDS patients. In summary, in the present study we have demonstrated that, at least in vitro, both fibroblasts and macrophages from MDS bone marrow (BM) are functionally abnormal. Such abnormalities include an increased apoptotic index, as well as a high production of both IL-6 and TNF-alpha.

Hematopoietic progenitor cells from patients with myelodysplastic syndromes: in vitro colony growth and long-term proliferation

It is known that the levels of hematopoietic progenitor cells (HPC) are greatly reduced in the majority of patients with myelodysplastic syndromes (MDS). To date, however, only limited information exists on the growth kinetics of these cells in long-term marrow cultures (LTMC), particularly in terms of erythroid and multipotent progenitors. In the present study, we have determined the HPC content in the bone marrow of 12 MDS patients and followed the proliferation kinetics of myeloid (including granulocyte, macrophage and granulocyte macrophage), erythroid (including early and late) and multipotent progenitor cells in LTMC throughout a 7-week culture period. Both the non-adherent and adherent fractions of the cultures were analyzed, so we were able to look at progenitor cells in suspension and those that physically associated to the stromal cell layer developed in culture. All 12 patients were grouped based on their FAB subtype and the in vitro growth of the HPC was analyzed accordingly. The results presented here indicate that in the majority of MDS patients, pronounced deficiencies exist both in the content and the long-term proliferation of marrow HPC. Such deficiencies were particularly evident for multipotent progenitors and those committed to the erythroid lineage, in which alterations in the maturation process also seem to be present. Our results suggest that, at least in some patients, HPC--besides showing an impaired proliferative capacity--lose their ability to adhere to the stromal cell layers developed in culture. RA patients showed the less affected in vitro HPC growth, whereas HPC from RAEB and RAEB-t showed a markedly deficient growth in culture. Interestingly, myelopoiesis was significantly increased in cultures of CMML patients. These results give some new insights into the biology of MDS-derived HPC.

Role of physiologic concentrations of stem cell factor in leukemic type growth of myelodysplastic CD34+ cells

The stem cell factor (SCF: a ligand for c-kit) plays a central role in the growth of myelodysplastic (MDS) progenitor cells with leukemic type growth. In this study, the role of physiologic concentrations of SCF on the proliferation and differentiation on MDS progenitor cells was further analyzed in the presence of combined cytokines. For this purpose, marrow CD34+ cells were purified up to 94% for 12 normal individuals and 90% for 18 MDS patients, using monoclonal antibodies and immunomagnetic microspheres. The purified CD34+ cells were cultured for 14 days with saturating doses of cytokines, including recombinant human macrophage colony stimulating factor (rM-CSF), granulocyte-CSF (rG-CSF), granulocyte/macrophage-CSF (rGM-CSF), interleukin-3 (rIL-3) and rSCF. The clonal growth of MDS CD34+ cells supported by a combination of all the above cytokines was then subdivided into the two patterns of leukemic or non-leukemic. The role of various concentrations of rSCF (0, 0.5, 5, 50 and 500 ng ml(-1)), with or without the above cytokines, in proliferation and differentiation of MDS CD34+ cells was analyzed in each group. The physiologic concentration of SCF at 5 ng ml(-1) significantly increased undifferentiated 'blast cell' colonies or clusters in leukemic type growth of MDS CD34+ cells over that seen in normal CD34+ cells. SCF is present in plasma at a level of ng ml(-1). This means that progenitor cells are continuously exposed to stimulation by SCF in vivo and that MDS leukemic cells have a growth advantage over normal blasts.

Growth characteristics of myelodysplastic CD34+ cells

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis entailing hyperproliferative and ineffective hematopoiesis associated with morphologic evidence of marrow cell dysplasia resulting in refractory cytopenia(s), and an increased risk of transformation into acute myeloblastic leukemia (AML). The administration of colony-stimulating factor(s) (CSFs) to patients with MDS increased blood neutrophil concentrations, in most patients, and it was anticipated to be of benefit to prevent infections. The progression to AML while being treated with CSFs has come under close scrutiny. In vitro studies are expected to produce more pertinent criteria for selection of patients who are likely to benefit, as well as the overall benefits of various therapies. For this purpose, in vitro colony assays are an excellent approach for investigation of the biologic characteristics of MDS progenitor cells. The stem cell phenotype CD34 is the one of the best markers of progenitor cells, and can be used for the purification of these cells to unify levels of maturation; a direct comparison of proliferative and differentiative capacity of MDS progenitor cells with normal CD34+ cells can thus be made. The properties of MDS CD34+ cells are described here in association with proliferation and differentiation, with special emphasis on the role of stem cell factor (a ligand for c-kit) in leukemic type growth of MDS CD34+ cells.

Blast colony forming cell-binding capacity of bone marrow stroma from myelodysplastic patients

A specific stroma function can be quantitatively assessed by counting the stroma-adherent blast cell colonies (CFU-BL) that are formed from normal plastic nonadherent mononuclear bone marrow cells (PNAMNC) after a short-term coincubation ("panning") with the preformed stromal layer. In order to obtain information of stroma function in myelodysplasia (MDS), the "CFU-BL-binding capacity" of stroma from normal bone marrow and from patients with MDS were compared. Stromal cell cultures were established from mononuclear bone marrow cells in microplate cultures cultured with or without 10(-6) M hydrocortisone. CFU-BL-binding capacity was studied by counting blast colonies seven days after panning, and the results were expressed as CFU-BL/10(3) PNAMNC. Normal marrow stromal layers bound CFU-BL only if they were cultured with hydrocortisone, while MDS stromal layers also bound CFU-BL in the absence of hydrocortisone. For further studies of the function of MDS stroma, the effect of growth factors (stem cell factor [SCF], G-CSF, interleukin 3 [IL-3] and their combinations) on CFU-BL binding by normal or MDS stroma has also been compared. Twenty-hour incubation of the stromal layers with a standard dose (100 ng/ml) of various hemopoietic growth factors (IL-3 alone or in combination with SCF, G-CSF alone or in combination with SCF) did not have any effect on CFU-BL binding by normal marrow stroma, but increased the CFU-BL binding by stromal layers from MDS bone marrow. These findings suggest that although stromal microenvironment in MDS is capable of supporting hemopoiesis, bone marrow stroma from MDS patients differs in some characteristics from the normal stroma.

Proliferation and differentiation of myelodysplastic CD34+ cells

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis involving hyperproliferative and ineffective hematopoiesis associated with morphologic evidence of marrow cell dysplasia resulting in refractory cytopenia(s), and an increased risk of transformation into acute myeloblastic leukemia (AML). The administration of colony-stimulating factor(s) (CSFs) to patients with MDS increased blood neutrophil concentrations, in most patients, and was also expected to be beneficial and to prevent infections. However, the progression to AML during the treatment with CSFs was suspected in some patients. Therefore, extensive in vitro studies were expected to lead to the establishment of criteria for selection of patients who are likely to benefit from CSF's as well as to establish the overall value of the different types of CSFs therapy. For this purpose, in vitro colony assays provide an excellent tool for investigating the biologic characteristics of MDS progenitor cells. However, conditions of the culture must be such that each progenitor can express its full potential for proliferation and differentiation. Because of the above, MDS progenitor cells cannot be used because they carry an impairment in proliferation and differentiation. To address this problem, one needs to know how many cells are being handled and the maximum numbers of colonies and clusters expected. CD34, a stem cell phenotype, is at present one of the best markers of progenitor cells, and can be used for purposes of purification. Using a defined number of CD34+ cells, it was feasible to make direct investigations on MDS progenitor cells. In this review the properties of MDS progenitor cells are described, in association with proliferation and differentiation, with special emphasis on the phenotypic subpopulations of MDS CD34+ cells.

Producton of tumor necrosis factor and granulocyte colony stimulating factor by bone marrow accessory cells in myelodysplastic patients

This paper reports on the production of tumor necrosis factor (TNF) and granulocyte macrophage colony-stimulating factor (GM-CSF) by cultured mononuclear adherent cells derived from bone marrow of 25 patients affected by myelodysplastic syndrome (MDS) of different FAB subtypes. Mean production of GM-CSF was much lower than in controls, without significant differences among different subtypes. Mean production of TNF was similar in MDS patients and in controls, but noteworthy differences were observed between patients with RA, RAEB and RAEB-t and patients with RARS and CMML. Growth of bone marrow granulocyte macrophage and erythroid progenitors did not correlate with TNF and GM-CSF production, although in MDS subtypes with higher GM-CSF levels, colony growth was slightly higher than in subtypes with lower GM-CSF production.

Proliferation and differentiation of myelodysplastic CD34+ cells in serum-free medium: II. Response to combined colony-stimulating factors

To investigate the role of colony stimulating factors (CSFs) in the proliferation and differentiation of progenitor cells from myelodysplastic syndromes (MDS), marrow progenitor cells from 18 MDS patients were highly purified using CD34 monoclonal antibody and immunomagnetic microspheres (MDS CD34+ cells). These cells were cultured in serum-free medium with various combinations of five colony stimulating factors (CSFs): recombinant human interleukin-3 (rIL-3), granulocyte/macrophage-CSF (rGM-CSF), granulocyte-CSF (rG-CSF), macrophage-CSF (rM-CSF), and erythropoietin (rEP). Among the tested CSFs, such as rM-CSF, rG-CSF, rGM-CSF and rIL-3, a combination of the first three CSFs was the most effective stimulus for the proliferation of non-erythroid MDS progenitor cells. An increase of undifferentiated "blast" cell colonies in 5/18 MDS patients occurred and these 5 patients belonged to the high-risk group. In the presence of these three CSFs, rIL-3 had no effect on the proliferation and differentiation of MDS CD34+ cells; however, IL-3 was efficient for the proliferation of MDS CD34+ cells to the erythroid lineage. rGM-CSF or rIL-3 alone did not efficiently support proliferation and differentiation of CD34+ cells. M-CSF is present in normal human serum at a concentration of 550 +/- 110 U/ml, a concentration exceeding that used in this study (100 U/ml). Therefore, in vivo administration of G-CSF combined with GM-CSF to MDS patients may be one of the most effective CSF combinations for proliferation of MDS progenitor cells to the non-erythroid lineage. However, the effect on the capacity for differentiation was minimal, especially in patients belonging to the high-risk group.

Impaired proliferation and differentiation of myelodysplastic CD34+ cells

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis entailing hyperproliferative and ineffective hematopoiesis resulting in refractory cytopenia(s), and increased risk of transformation into acute myeloblastic leukemia (AML). The widely used classification defined by the French-American-British group (FAB) recognizes 5 cytological subtypes of different prognosis, based essentially on the presence and the frequency of marrow blasts. The percentage of marrow blasts does not exceed 30%, hence, direct investigations of biological and biochemical events of MDS blast cells have been hampered. The CD34 antigen is currently unique in its narrow specificity of expression on human lymphohematopoietic progenitor cells. This cell membrane phosphoglycoprotein has been used for immunologic blast cell purification, notwithstanding the frequency of marrow blasts, and has provided a set of tools for investigations of MDS i.e. a direct comparison of the nature of blast cells in each of the MDS subtypes, using immunologic, biologic, biochemical and molecular biological methodology. A combination of serum-free medium and a purification method for blast cells provided evidence that the progenitor cell growth abnormalities in these disorders involve a defect in the capacity of progenitor cells to respond to stimulation with growth factor(s), and has presented direct evidence for the manner in which myelodysplastic CD34+ cells are impaired.

Impairment of GM-CSF production in myelodysplastic syndromes

In this study we evaluated the production of granulocyte/macrophage-colony stimulating factor (GM-CSF), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) by enriched bone marrow (BM) macrophages in 15 patients affected by myelodysplasia and 20 normal BM donors. The presence of GM-CSF, IL-6 and TNF-alpha in the culture supernatants of BM macrophages was detectable only after stimulation with lipopolysaccharide (LPS), whereas no differences were present in the amount of IL-6 and TNF-alpha between myelodysplastic patients and normal controls, GM-CSF production appeared eight-fold reduced in BM macrophage culture supernatants from myelodysplastic patients with respect to normal controls. After further experiments, we concluded that the impaired release of GM-CSF by BM macrophages could not be due to a different production kinetic in myelodysplastic patients. Moreover, the number of multipotent (CFU-GEMM), granulocyte/macrophage (CFU-GM) and erythroid (BFU-E) progenitors was significantly impaired in myelodysplastic patients. In conclusion, we demonstrated that the production of GM-CSF by purified adherent cells from MDS patients is markedly impaired in spite of the peripheral blood cytopenia. This selective defect in GM-CSF production, along with an intrinsic defect of haematopoietic progenitor cells, might contribute to the impairment of haematopoiesis always observed in myelodysplastic patients.

Proliferation and differentiation of myelodysplastic CD34+ cells in serum-free medium: response to individual colony-stimulating factors

The presence of serum or contaminant cells may alter clonal development of haematopoietic progenitor cells in vitro. To investigate the pathogenesis of myelodysplastic syndromes (MDS), marrow progenitor cells from 13 MDS patients were highly purified using monoclonal antibodies including CD34 and immunomagnetic microspheres. The cells positive for CD34 in the purified cells were in the range from 87% to 98%. These purified cells were cultured in serum-free medium with individual colony stimulating factors (CSFs) to investigate whether CD34+ cells from MDS patients have abnormal responses to individual CSFs. Dose response experiments with the purified CD34+ cells and recombinant human macrophage-CSF (rM-CSF), granulocyte-CSF (rG-CSF), granulocyte/macrophage-CSF (rGM-CSF), interleukin-3 (rIL-3) or erythropoietin (rEP) were performed in serum-free fibrin clots in 11 patients. Five patients showed a diminished response to rG-CSF and one patient to rEP. In the remaining six patients the purified CD34+ cells did not respond to a stimulation of any individual CSFs. The results indicate that the progenitor cell growth abnormalities in these disorders involve a defect in the capacity of progenitor cells to respond to stimulation with G-CSF, and present direct evidence for the manner in which myelodysplastic CD34+ cells are impaired.

Myelodysplastic syndromes: immunohistochemical and morphometric evaluation of proliferative activity in erythropoiesis and endoreduplicative capacity of megakaryocytes

An immunohistochemical and morphometric analysis was performed on bone marrow trephine biopsies in 40 patients with primary myelodysplastic syndromes (MDS) to evaluate the proliferative activity in erythropoiesis and the endoreduplicative capacity of megakaryocytes. Control groups included normal bone marrow and marrow from cases presenting with pernicious anaemia. Double-immunostaining was applied with a monoclonal antibody (PC10) directed against proliferating cell nuclear antigen (PCNA), followed by antibodies against glycophorin C (Ret40f) or platelet glycoprotein IIIa (Y2/51-CD61) for the identification of the erythroid and megakaryocytic cell lineage. Comparison with normal bone marrow showed a reduction of erythropoiesis accompanied by an increase in atypical (micro-) megakaryocytes. Erythroid precursors displayed significant enhancement of PCNA-immunostaining. Megakaryocytes showed no increase in the relative frequency of PC10-positive cells (PCNA-labelling index). In pernicious anaemia, predominance of macrocytic-megaloblastoid erythropoiesis was associated with a striking increase in PCNA-labelling. Cell kinetic studies in this disorder revealed an abnormal arrest, particularly in S-phase which generates an over-expression of PCNA. Similar conditions were believed to be present in MDS with secondary folate deficiency. This mechanism explains the relatively high rate of positively-reacting pro- and erythroblasts which is not invariably accompanied by an increase in cell proliferation. Determination of megakaryocyte size and PCNA-staining capacity resulted in a significant increase in PC10-positive cells among micromegakaryocytes. Our findings on this cell lineage are in keeping with the assumption of a block in endoreduplicative activity at higher ploidy levels, associated with an apparently not-deregulated endomitosis in small-sized megakaryocytes of lower ploidy stages.

Myelodysplastic syndromes. Pathogenesis, diagnosis and treatment

Our understanding of the biology of leukemia and myelodysplasia is still only partial. The diagnosis of myelodysplasia is often based on quantitative and qualitative findings in the peripheral blood and bone marrow. These findings are often shared by other disorders. There is a need for sensitive and inexpensive laboratory tests to determine clonality and karyotypic abnormalities in this disorder. Future classifications of these syndromes will need to be based on morphologic and biologic markers that are closely linked to disease progression, response to treatment, and survival. Our limited understanding of the pathogenesis of MDS decreases the specificity and effectiveness of our therapeutic interventions. Agents that are minimally toxic such as CRA, danazol, 1,25-dihydroxyvitamin D3, androgens, and pyridoxine are seldom useful. Antileukemic therapy and allogeneic bone marrow transplantation have a major role to play in patients younger than 45 years of age; in older patients these treatment modalities remain controversial because of their toxicity. Hematopoietic growth factors, used alone or in combination, may improve the quality of life and improve survival of patients with MDS. Growth factors may also decrease treatment-related mortality associated with chemotherapy and bone marrow transplantation and render these treatment modalities available for a higher percentage of patients. The development of more specific differentiating agents may permit hematopoietic differentiation while minimizing side effects.

Myelodysplastic syndromes (refractory anemia). A perspective of the biologic, clinical, and therapeutic issues

The myelodysplastic syndromes (MDS) are a diverse group of hematologic disorders that have an abnormality in differentiation of the hematopoietic stem cell resulting in varying degrees of peripheral blood cytopenias. The author reviews the hematologic and clinical aspects of MDS, summarizes the recent pertinent aspects of the advances in our understanding of the disease, and explores the current approaches in the new treatment programs.

Risk assessment in myelodysplastic syndromes: value of clinical, hematologic and bone marrow histologic findings at presentation

We analyzed the prognostic value of clinical, hematologic and bone marrow (BM) histologic findings at presentation in 94 patients with myelodysplastic syndromes (MDS) (28 RA; 2 RARS; 34 RAEB; 6 CMML; 24 RAEB-t). With survival as the dependent variable, stepwise multivariate analysis indicated as the prognostically most important factors among the MDS taken as a whole: latency from the first symptoms to diagnosis, age, and percentage of BM blasts. In each main MDS group the most unfavorable initial characteristics were: 1) low Hb, no macro-megaloblastosis, male sex for RA/RARS; 2) low Hb and low platelet levels for RAEB/CMML; 3) granuloblastic hyperplasia and high BM blastosis for RAEB-t. Of the BM histologic parameters, only the percentage of blasts had significant prognostic value. Histologic assessment of BM blastosis, however, did not differ statistically from that based on cytologic examination of BM smears, so that marrow histology seemed not essential for initial prognostic assessment in MDS patients. The finding of abnormal localization of immature precursors (ALIP) in BM biopsies was associated with a negative trend without reaching statistical significance. Using four objective parameters of proven significance (age, Hb, platelets, and BM blasts) we devised a staging system of immediate clinical utility for prognostic stratification and risk-adapted therapeutic choices.

Bone marrow in vitro growth and cytogenetic studies in patients with FAB-classified primary myelodysplastic syndromes

Thirty-eight consecutive patients with a FAB-classified primary myelodysplastic syndrome (MDS) were investigated for in vitro growth of colony-forming units for granulocyte-macrophage precursors (CFU-GM) and cytogenetic analysis of bone marrow cells. Abnormal CFU-GM growth was found in 30 patients (79%), and clonal chromosome abnormalities were found in 13 patients (34%). The eight patients who showed normal CFU-GM growth were either cytogenetically normal (n = 5), or had a 5q-deletion (n = 3) as single or dominating karyotypic abnormality. Among the 30 patients with reduced or no colony growth, ten patients had a clonal chromosome abnormality. Leukemia developed in eight patients. None of them grew any CFU-GM colonies, and three of them were cytogenetically abnormal at the time of diagnosis of MDS. Analysis of the bone marrow in vitro growth for CFU-GM and the karyotype in patients with MDS emphasizes the close relationship between these disorders and manifest acute leukemia. Subgroups of MDS may be defined by a cytogenetic classification (e.g., the 5q-syndrome), and the CFU-GM growth pattern can be of value for predicting leukemic transformation.

Myelodysplastic syndromes

A cure for MDS has yet to be found. The aim of therapy is to attempt to restore normal hematopoiesis and prevent evolution to acute leukemia. The major trend is supportive care. Blood counts and bone marrow aspirations are taken to evaluate the disease, and transfusions of blood products and antibiotics are given when necessary. A new encouraging modality of therapy is the use of hematopoietic growth factors to reverse cytopenias. As there is no curative treatment for MDS, the patient is likely to be offered investigational drugs either singly or in combination. Future trends in the treatment of MDS will be combinations of agents including biological agents with retinoic acid or vitamin D, low-dose Ara-C, the interferons, and colony-stimulating factors.

Preliminary studies on melatonin in the treatment of myelodysplastic syndromes following cancer chemotherapy

Experimental studies have suggested that the pineal hormone melatonin, in addition to its documented antineoplastic action, plays a role in the physiological regulation of blood cell proliferation. Based on these data, we evaluated the clinical effects of melatonin therapy in patients with myelodysplastic syndrome (MDS) secondary to cancer chemotherapy for primary neoplasms. The study was carried out on six patients, and melatonin was given orally at a dose of 20 mg/daily, following a schedule prepared to reproduce the circadian rhythm of the pineal hormone. A transient improvement in platelet and neutrophil count was achieved in two of five patients with thrombocytopenia and in two of four patients with neutropenia before therapy, respectively, while no effect was seen on hemoglobin concentration. Mean survival time was 12.5 months, and a long survival, greater than 30 months, was achieved in two of six patients. These preliminary results seem to suggest that melatonin may have a role in the treatment of MDS induced by previous cancer chemotherapy.

The combined effects of Il-3, GM-CSF and G-CSF on the in vitro growth of myelodysplastic myeloid progenitor cells

The decreased or absent in vitro colony formation in response to single recombinant haematopoietic growth factors has been reported previously. Here we report on the effects of the combination of interleukin 3 (Il-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) and the effect of the conditioned medium of the giant tumour cell line (GCT-CM) on the proliferation of myelodysplastic (MDS) marrow myeloid progenitor cells and normal bone marrow (NBM) controls. Colony growth was most effectively sustained by GCT-CM and G-CSF in normal bone marrow (NBM) cultures. GM-CSF and Il-3 were less effective in inducing myeloid granulocytic colony growth, whereas the effects of Il-3 and GM-CSF were found to be approximately additive. The number of NBM granulocytic colonies induced by G-CSF and GCT-CM stimulation were comparable, whereas this granulocyte colony stimulating activity could be neutralized by anti-G-CSF antibodies. In addition GCT-CM was found to contain burst promoting activity, which could be neutralized by anti-Il-3 antibodies. Il-3 did not enhance the G-CSF activity in NBM cultures. No additive effect of stimulation with the combination of Il-3 and GM-CSF was observed in MDS marrow cultures, suggesting that these growth factors act on an identical progenitor cell population in MDS. G-CSF stimulated the growth of significantly lower colony numbers than GCT-CM, in contrast to NBM cultures. The decreased granulocytic colony formation of MDS marrow cells could clearly be enhanced by co-stimulation with Il-3. These results suggest that MDS myeloid progenitor cells require the exposure to both a pluripotent colony stimulating factor, like Il-3, and a lineage specific factor, like G-CSF, for optimal proliferation.

Analysis of human dysplastic haematopoiesis in long-term bone marrow culture

In this paper we have analysed the behaviour of myelodysplastic marrow in a long-term bone marrow liquid culture system (LTBMC) from eleven patients with myelodysplastic syndromes with regard to cellularity, day-7 and day-14 CFU-GM growth, cluster formation, adherent cells and CFU-F formation. An altered CFU-GM pattern was found in 64% of cases at diagnosis, while normal growth was seen in the remaining cases, all of which were affected by refractory anaemia. The levels of CFU-GM, as well as cellularity, were reduced in myelodysplastic marrows compared to normal controls over the whole duration of LTBMCs. Cases with a normal CFU-GM level at diagnosis also showed pathological behaviour when examined in LTBMC. The duration of dysplastic haematopoiesis was significantly shorter than that of controls. The proliferative ability of CFU-F was reduced in 50% of cases as shown by replating experiments. In conclusion, myelodysplastic marrow shows an abnormal behaviour in LTBMC, even in those cases which present normal CFU-GM growth at diagnosis.

Regulatory abnormalities in the marrow of patients with myelodysplastic syndromes

Regulation of haemopoiesis in the marrow of patients with myelodysplastic syndromes (MDS) was evaluated by assaying (1) the production of haemopoietic regulators acting upon multipotent and committed progenitors by MDS marrow cells, and (2) the responsiveness of MDS marrow progenitors to stimulation with granulocyte colony-stimulating factor (G-CSF). The levels of multipotent progenitor cell colony-stimulating activity (CFU-GEMMCSA) in 7 d bone marrow-conditioned medium (BMCM) from MDS patients were markedly reduced as compared to controls. MDS BMCM also exhibited reduced levels of burst-promoting activity (BPA) for primitive erythroid (BFU-E) progenitors. Both CFU-GEMMCSA and BPA detected in BMCM were completely neutralized by antibodies directed against interleukin-3. MDS BMCM exhibited markedly reduced levels of murine-active CSA. This activity was partially neutralized by anti-CSF-1 antibodies. Levels of regulators in BMCM of refractory anaemia (RA), sideroblastic anaemia. RA with excess blasts, and chronic myelomonocyte leukaemia were virtually the same. CFU-GEMM and BFU-E growth in MDS marrow (n = 9) was markedly reduced. A 5-fold saturating dose of G-CSF induced an approximately 2-fold increase in CFU-GEMM in four of eight MDS and a 1.5-fold increase of BFU-E in five of nine MDS, but not in control (n = 5) marrow cell cultures. Impaired haemopoiesis in MDS marrow may be related to abnormalities both in regulator production by marrow accessory cells and in regulator responsiveness of multipotent and committed progenitors.

Natural killer cell-mediated inhibition of bone marrow colony formation (CFU-GM) in refractory anaemia (preleukaemia): evidence for patient-specific cell populations

The role of peripheral blood mononuclear cells (PB-MNC) on the growth of bone marrow (BM) CFU-GM was investigated in refractory anaemia (RA) patients. Whereas normal donor PB-MNC were found to inhibit autologous day 7 CFU-GM, PB-MNC from RA patients exhibited little modulatory effect on autologous or allogeneic day 7 CFU-GM. In contrast, patient PB-MNC inhibited autologous CFU-GM at day 10 at a time where no significant inhibition was seen in the PB-MNC/RA CFU-GM combination. The identity of the inhibitory cells was investigated using anti-T8+ and anti-N901+ subsets purified by immune-rosette depletion with a panel of monoclonal antibodies. The activity of these subsets was tested on immature myeloid cells enriched for MY7+ cells, and it was found that cells highly enriched for NK cells were responsible for the inhibition. Further support for NK cells as the inhibitory cells was obtained in experiments where a positive correlation between the level of PB NK cytotoxicity against K562 cells and the degree of CFU-GM inhibition was demonstrated. Thus, these data suggest the presence of a specialized subset of NK cells with a capacity to inhibit autologous CFU-GM. Since RA is a potentially premalignant disease, in which a significant number of cases transform into AML, these findings also suggest a physiological role for NK cells in suppression of newly arisen clonogenic cells at least in early stages of the disease.

Deficiency of pluripotent hemopoietic progenitor cells in myelodysplastic syndromes

Pluripotent (CFU-MIX), erythroid (BFU-E) and granulocyte/macrophage (CFU-GM) progenitor cells were examined in bone marrow (BM) from 23 patients with myelodysplastic syndromes (MDS). Patients were grouped according to the FAB classification: Refractory anemia (RA), n = 3; RA with ring sideroblasts (RARS), n = 3; RA with excess of blasts (RAEB), n = 8; RA with excess of blasts in transformation (RAEBt), n = 7; chronic myelomonocytic leukemia (CMML), n = 2. In FAB groups RA, RARS, RAEB and RAEBt CFU-GM concentrations were normal or decreased but both CMML-patients had increased CFU-GM values. Abnormal cluster growth was observed in 9 of 23 MDS-patients. BFU-E colony formation was subnormal in all cases. Mixed-colony assay values were at the lower limit of controls in one patient and decreased in the remaining 22 MDS-patients. A similar growth pattern of hemopoietic progenitor cells was observed in 19 patients with acute nonlymphocytic leukemia (ANLL), who were studied for comparison. These data suggest a quantitative or qualitative/functional defect of the pluripotent progenitor cell compartment as the major cause for the cytopenia in MDS-patients.

Enrichment of haemopoietic progenitor cells from the marrow of patients with myelodysplasia

Myeloid and erythroid progenitors from myelodysplastic marrows have been separated from accessory cell populations likely to influence their in-vitro growth. Myeloid colony-forming cells were enriched 23-fold and erythroid progenitors 5-7-fold but, in both cases, retained their abnormal growth characteristics. After enrichment and removal of lymphocytes and monocytes, erythroid burst formation became markedly more dependent on the addition of 5637 bladder carcinoma conditioned medium as an exogenous source of haemopoietic growth factors. This suggests that lymphocytes and monocytes usually support erythropoiesis in cultures of myelodysplastic marrow and demonstrates that erythroid burst-forming progenitor cells from myelodysplastic patients can respond to these populations in vitro. Haemopoietic failure in myelodysplasia appears to result from a defect within the preleukaemic clonogenic cell, rather than from an aberration in exogenous factors. The procedure outlined here can be used as a first step towards the isolation of these abnormal progenitors.

Effects of recombinant human granulocyte-macrophage colony-stimulating factor in patients with myelodysplastic syndromes

The myelodysplastic syndromes are characterized by ineffective hematopoiesis and refractory cytopenias. In an attempt to improve hematopoiesis, we administered recombinant human granulocyte--macrophage colony-stimulating factor (GM-CSF) to eight patients with myelodysplastic syndrome, as part of a Phase I trial. The GM-CSF was given by continuous intravenous infusion daily for two weeks and then again after a two-week rest period. Over the entire dose range tested (30 to 500 micrograms per square meter of body-surface area), treatment was associated with marked increases in peripheral-blood leukocytes (5- to 70-fold), including granulocytes (5- to 373-fold), in all eight patients. The absolute number of monocytes, eosinophils, and lymphocytes increased in all patients. Three of eight patients also had 2- to 10-fold increases in platelet counts and improvement in erythropoiesis, with the result that two of three patients who had required red-cell and platelet transfusions no longer needed them (at 20 to 27 weeks of follow-up). Treatment was also associated with increased marrow cellularity and a decreased percentage of blasts in the bone marrow of patients with excess blasts, resulting in an increase in the ratio of differentiated myeloid cells to immature myeloid cells. We observed relatively few side effects, but bone pain was dose-limiting when it was associated with high white-cell counts. Our results showed that GM-CSF is a potent stimulator of hematopoiesis in vivo and may produce hematologic improvement in the short term (8 to 32 weeks of observation) in patients with myelodysplastic syndrome. More experience, with longer follow-up periods, will be necessary to assess the long-term safety and efficacy of this new treatment.

Erythroid and myeloid maturation patterns related to progenitor assessment in the myelodysplastic syndromes

Patterns of erythropoiesis and granulopoiesis were studied in 15 patients with myelodysplastic syndromes and in one with smouldering leukaemia by correlating CFU-C, BFU-E and CFU-E cloning efficiency with erythroid and myeloid maturation indices derived from quantitative 14C-autoradiography and with ferrokinetics. Maturation index of a cell lineage was defined as the ratio of cell production rate increase from the first to the last proliferative compartment over the corresponding normal value. The myeloid maturation index was reduced in all cases, but CFU-C progenitor frequency was increased by a factor of 3. Erythroid maturation index was also reduced in most cases, and BFU-E progenitor frequency was reduced by a factor of 2. Similarly, CFU-E cloning efficiency corrected for the erythroid maturation index was 2.5-10-fold lower than normal. Comparison of the erythroid maturation index with ferrokinetics revealed a constant ratio of ineffective erythropoiesis with a maturation disturbance in the proliferative pool twice that in the non-proliferative pool. These findings indicate basic qualitative and quantitative abnormalities and a difference in the patterns of production of erythroid and myeloid cells in the myelodysplastic syndromes: Myeloid progenitors are increased in number but their maturation is grossly abnormal. On the other hand, the apparent reduction in erythroid progenitors and the reduced erythroid maturation index are attributable to both premature cell death of the more mature erythroblasts and an increased proerythroblast proliferation, i.e. extra divisions in the proerythroblast compartment at the expense of maturation.

Biology of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a diverse spectrum of disorders ranging from refractory anemia to a preleukemic state. Peripheral cytopenias, cellular marrow, dysplasias and dysfunctions of myeloid and lymphoid cells constitute hematological hallmarks, and are caused by ineffective hemopoiesis. Investigations of cell cultures and cellular functions indicate that the disease originates in a stem cell pluripotent to all myeloid cells and possibly lymphoid cells as well. The disease commonly runs a chronic indolent course, often terminating in acute leukemia or nonleukemic death, notably infections and/or hemorrhage due to cytopenias and cellular dysfunctions. Clonal expansion or clonal evolution appears to be related to the disease progression with a greater degree of malignancy. However, the initial sequence of events causing damage to stem cells is still undefined.

The management of leukaemia in the elderly

Leukaemia is relatively common in the elderly compared to the general population, with over half of all cases of leukaemia occurring in patients aged 65 and over. Special problems are associated with treating patients in this age group. The leukaemias may be intrinsically different, in part because of the high incidence of preceding myelodysplasia. There is increased likelihood of coincident disease. There is lower tolerance to toxic complications, such as infection and bleeding, associated with a decreased resilience of normal haematopoiesis. There is more difficulty in obtaining intravenous access in elderly patients. These problems render patients ineligible for marrow transplants. Myelodysplastic syndromes occur predominantly in the elderly. There are a number of myelodysplastic syndromes now identified, each with its characteristic natural history. Management decisions are based on accurate diagnosis of the specific syndrome, consideration of prognostic features, a period of observation, and conservative treatment principles. More than half the cases of acute myeloblastic leukaemia also occur in the elderly. Prognostic factors must be examined and the literature carefully scrutinized for results pertinent to the elderly patient. In some patients treatment may be justifiably withheld, others may benefit from low dose cytosine arabinoside and some patients should receive aggressive combination chemotherapy. Management of the chronic leukaemias in the elderly is a less controversial area. Chronic lymphocytic leukaemia is the most common of the leukaemias in this age group. Prognostic factors can be determined using staging criteria. observation alone is indicated in many patients. Chlorambucil and prednisone are the most widely used drugs for symptomatic disease. Aggressive combination chemotherapy may benefit a few patients with advanced or refractory CLL. Hairy cell leukaemia is a rare disorder but many of the patients are over age 65. The elderly male patient may have a particularly benign course and require no therapy. Splenectomy is the standard first line of therapy, but recombinant alpha-interferon is sufficiently effective and non-toxic that it should be the treatment of choice in some patients. Deoxycoformycin is also effective in preliminary trials and may soon be routinely indicated. It is not often appreciated that half of all patients with chronic myelogenous leukaemia are aged 65 and over.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of cytosine arabinoside on CFU-GM from patients with myelodysplastic syndrome

CFU-GM clonal growth was examined in bone marrow from patients with myelodysplastic syndrome (MDS) in the presence of Ara-C at 10(-8) M and 4 X 10(-8) M and the response compared to the effect on progenitors from normal subjects. Seventy-three percent of marrow cultures from patients with MDS showed colony growth below the 95% confidence limits for normal subjects in the presence of 10(-8) M Ara-C. At 4 X 10(-8) M Ara-C 43% of marrow cultures had subnormal colony growth. These results suggest that CFU-GM from patients with MDS may have a greater than normal sensitivity to Ara-C.

Specific minor chromosome deletions consistently occurring in myelodysplastic syndromes

Forty-two patients with refractory anemia with or without sideroblasts have been investigated cytogenetically one to nine times (mean, 3) over a period of 1-36 months (mean, 16). The initial investigation showed numerical and/or major structural abnormalities [t(3;3), 5q-, -7, or 7q-, 11q-] in nine patients (21%). In addition, minimal terminal deletions were observed in 2p, 8p, 9p, 11p, 12p, 17p, 17q, 20q, and Xp. The detection of these deletions, which have not been reported earlier, was due to consistent application of the high resolution technique, G-banding without trypsin, and metaphase photography on large size negatives. Each deletion occurred as a clone on one or more occasions in 1-17 patients (mean, 7). One or other clonal minimal deletion was observed in 32 patients (76%). Preliminary indirect evidence indicates that alone or together with other factors the deletions promote leukemic transformation of refractory anemia.

Histopathological and hematological findings in myeloid leukemia induced by a new feline leukemia virus isolate

Myeloid leukemia was induced by a new feline leukemia virus isolate FeLV-AB/GM-1 in a high proportion of cats. The latency period was short. Three to 5 weeks after infection early changes were detectable in the bone marrow, and cats developed leukemia 5 to 8 weeks after infection. The results of the present histological and cytological studies suggested that there were two stages in the development of leukemia. The first stage appeared to be equivalent to the syndrome of bone marrow dysplasia or preleukemia which, however, converted rapidly to leukemia. Cytopenia(s) were the main hematological findings in all preleukemic and leukemic cats. White blood cell counts were low or normal, but the number of leukemic and abnormal cells increased in the peripheral blood with the progression of the disease. This reliable model system lends itself to further studies to elucidate the pathogenesis of myeloproliferative disorders.

Prognostic significance of some clinical, morphological and cytogenetic findings in refractory anaemia (RA) and RA with sideroblasts

In 27 patients initially diagnosed as refractory anaemia (RA) or RA with sideroblasts (RA-S) according to the FAB-classification a number of clinical, morphological and cytogenetic parameters were correlated for prognostic significance. From these correlations it emerged that severe cytopenia is centrally positioned with regard to clinical course in RA and RA-S. Positive correlations were found to initial diagnosis, clonal cytogenetic abnormalities, progression to RA with an excess of blasts (RAEB) or acute myeloid leukaemia (AML), the percentage of bone marrow blast cells and prolonged half life for radioactively labeled iron. The degree of peripheral blood granulocytopenia, alone, was correlated to bone marrow hypoplasia. Moreover, the frequency of abnormal karyotypes was inversely correlated to bone marrow cellularity and proportional to the frequency of bone marrow blast cells. From these relationships it may be proposed that chromosome abnormalities are associated with prolonged blast cell generation times and inhibition of blast cell maturation resulting in reduced marrow cellularity and blast cell accumulation, and, in the peripheral blood, falling percentages of neutrophil granulocytes. With the blast cell accumulation the bone marrow cellularity again becomes hyperplastic and the preleukaemic condition is transformed into RAEB or AML.

The concept of preleukemia: clinical and laboratory studies

Thirty-five years ago, a handful of astute clinical hematologists began to notice that some of their patients with acute nonlymphocytic leukemia had a history of a preceding ill-defined hemopathy. This "preleukemic" hemopathy was increasingly reported anecdotally and through careful retrospective analyses. In more recent prospective studies, this syndrome has been relatively well defined. Indeed, it is widely accepted that there exists a hematopoietic abnormality not recognizable as classical, overt, acute nonlymphocytic leukemia, which, nonetheless, can represent an early phase of leukemia. In this manuscript, the author reviews the original case reports, the initial retrospective studies, and the prospective studies which have clarified some of the clinical and laboratory features of the preleukemic syndrome. The notion that the preleukemic syndrome represents an established neoplastic process will be reviewed with special attention to assessment of clonal hematopoiesis, cytogenetic studies, and clonal evolution. Studies on induced leukemia and preleukemia in experimental animals and humans will be reviewed as will be the semantic issues which have complicated our ability to compare interinstitutional studies. A simple classification scheme of the myelodysplastic syndromes will be presented as will be a framework agenda for future studies on the pathophysiology of these syndromes.

Myelodysplastic syndromes: pathogenesis, functional abnormalities, and clinical implications

The myelodysplastic syndromes represent a preleukaemic state in which a clonal abnormality of haemopoietic stem cell is characterised by a variety of phenotypic manifestations with varying degrees of ineffective haemopoiesis. This state probably develops as a sequence of events in which the earliest stages may be difficult to detect by conventional pathological techniques. The process is characterised by genetic changes leading to abnormal control of cell proliferation and differentiation. Expansion of an abnormal clone may be related to independence from normal growth factors, insensitivity to normal inhibitory factors, suppression of normal clonal growth, or changes in the immunological or nutritional condition of the host. The haematological picture is of peripheral blood cytopenias: a cellular bone marrow, and functional abnormalities of erythroid, myeloid, and megakaryocytic cells. In most cases marrow cells have an abnormal DNA content, often with disturbances of the cell cycle: an abnormal karyotype is common in premalignant clones. Growth abnormalities of erythroid or granulocyte-macrophage progenitors are common in marrow cultures, and lineage specific surface membrane markers indicate aberrations of differentiation. Progression of the disorder may occur through clonal expansion or through clonal evolution with a greater degree of malignancy. Current attempts to influence abnormal growth and differentiation have had only limited success. Clinical recognition of the syndrome depends on an acute awareness of the signs combined with the identification of clonal and functional abnormalities.

CFU-gm assay, cytochemical and electron microscopic studies in agar in patients with preleukemic syndrome and aplastic anemia

Thirty-seven patients with chronic cytopenia were studied using a CFU-gm assay in agar. Cell proliferation was evaluated on days 2, 3, 5, 7, and 10 of incubation. Growth patterns were different in cultures of hematologically healthy persons versus patients with preleukemic syndrome (PL) and aplastic anemia (AA). Three types of PL syndrome and two types of AA (C1 and C2) were distinguished. Bone marrow dysfunction was evaluated further using cytochemistry and electron microscopy to morphologically study cell proliferation in vitro. Cytochemical staining performed in agar demonstrated well-defined maturation defects in myelopoietic precursor cells from the bone marrow of PL patients. Electron microscopic findings of Auer-body-like inclusions in "statu nascendi" in the vacuoles of preleukemic cells supported our results. PL patient groups at high risk for development of overt leukemia and patients with grave prognosis in AA were distinguished. Our results are relevant for the clinical diagnosis and prognosis of patients with cytopenia.

Predictive value of bone marrow cultures in 48 patients with acute myeloblastic leukaemia or myelodysplasia both secondary to treatment of other malignant diseases

The growth pattern of bone marrow cells in agar cultures was studied in 48 patients with acute myeloblastic leukaemia or myelodysplasia, secondary to cytoreductive treatment, and compared to other laboratory findings. At diagnosis the status of the patients was: acute myeloblastic leukaemia (AML) in 9, acute myeloproliferative syndrome (AMS) in 13 and preleukaemic syndrome (PL) in 26 patients. 20 of the 39 patients with AMS and PL developed acute leukaemia, 15 of them within 1 year. 15 died of complications to cytopenia and only 4 are still alive and without leukaemia, observed from 8 to 55 months. Progression to AML was predicted from the agar cultures by increased cluster growth. Among 18 patients with increased cluster growth at diagnosis 14 subsequently developed AML. Among 21 patients with normal or decreased cluster growth at diagnosis 6 patients developed AML, but after conversion of the growth pattern to increased cluster growth. In 2 patients the increased cluster growth disappeared spontaneously and the patients are long-term leukaemia-free survivors. Colony growth pattern, conversely, was not related to leukaemic progression. Only 1 patient had normal growth pattern at diagnosis with respect to both clusters and colonies. Survival was short, with a median of about 7 months, unrelated to growth pattern and leukaemic progression.

Myelodysplastic syndromes. A clinical and pathologic analysis of 109 cases

A total of 109 patients with myelodysplastic syndromes (MDS) was analyzed to determine the clinical and pathologic features of the five recently defined French-American-British Cooperative Group (FAB) subtypes, and to assess the utility of this classification system in predicting survival, evolution to acute nonlymphocytic leukemia (ANLL), and cause of death. All patients with MDS presented with anemia; additional cytopenias were present in patients with refractory anemia with excess blasts (RAEB), chronic myelomonocytic leukemia (CMML) and refractory anemia with excess blasts in transformation to ANLL (RAEB/Tr). Thirty-two patients received some form of antileukemic therapy for MDS. ANLL developed in 16 of the 77 remaining untreated patients, including 18% (2/11), 0% (0/21), 22% (5/23), 33% (2/6), and 44% (7/16) of patients with refractory anemia (RA), refractory anemia with ring sideroblasts (RARS), RAEB, CMML, and RAEB/Tr, respectively (P = 0.02). The FAB subtype was highly predictive of survival with median survivals ranging from 71 months for RARS to 5 months for RAEB/Tr (P = less than 0.0001). Patients with RAEB, CMML, and RAEB/Tr frequently died of direct consequences of MDS, while patients with RA and especially RARS generally survived or died from unrelated disorders (P = less than 0.0001). MDS encompass a spectrum of disorders. RA and RARS, are relatively indolent and often do not lead to the patient's demise. RAEB, CMML, and RAEB/Tr are aggressive disorders which are often responsible for the patient's death whether or not actual progression to overt leukemia occurs. FAB subtype predicts survival, evolution to ANLL, and cause of death, although the five morphologic subtypes appear to separate into only two disease groups, especially with regard to survival and cause of death.